A flat-panel CRT display basically consists of an electron-emitting device and a light-emitting device. The electron-emitting device contains electron-emissive elements that emit electrons across a relatively wide area. The electrons are directed toward light-emitting regions distributed across a corresponding area in the light-emitting device. Upon being struck by the electrons, the light-emitting regions emit light which produces an image on the viewing surface of the display.
The electron-emitting device contains a plate, commonly referred to as the backplate, over which the electron-emissive elements are situated. The light-emitting device likewise contains a plate, commonly referred to as the faceplate, over which the light-emissive regions are situated. The backplate and faceplate are connected together, typically through an outer wall, to form a sealed enclosure.
For a flat-panel CRT display to operate properly, the sealed enclosure needs to be at a high vacuum. Contaminant gases in the enclosure can degrade the display and cause various problems such as reduced display lifetime and non-uniform display brightness. Hence, it is imperative that a flat-panel CRT display be hermetically (airtight) sealed, that a high vacuum be provided in the sealed enclosure when the display is sealed, and that the high vacuum be maintained in the display subsequent to sealing.
To maintain the requisite high vacuum during and after the sealing operation, a flat panel CRT display is typically provided with getter (or gettering) material that sorbs contaminant gases. The ability of a getter to sorb contaminant gases typically increases as the surface area of the getter increases. It is generally desirable that the active imaging area of a flat-panel CRT display be a large fraction of the display's overall lateral area. Accordingly, a common design objective is to configure the getter material so that is has a large surface area without significantly increasing the display's overall lateral area.
FIGS. 1–4 illustrate four prior art arrangements for providing getter material in light-emitting devices of field-emission flat-panel CRT displays, commonly referred to as field-emission displays (“FEDs”). The light-emitting device of FIG. 1 is disclosed in U.S. Pat. Nos. 5,606,225 and 5,628,662. U.S. Pat. No. 5,498,925 discloses the light-emitting device of FIG. 2. The light-emitting devices of FIGS. 3 and 4 are disclosed in U.S. Pat. No. 5,945,780.
The light-emitting device of FIG. 1 contains transparent planar substrate 10, transparent electrically conductive anode layer 12, region 14 of luminescent material, and barrier structures 16 arranged as parallel ridges that laterally separate luminescent regions 14. Barrier structures 16 preferably consist of material which is opaque across the visible spectrum. Deflection electrodes 18 are respectively situated on structures 16. Electrodes 18 are controlled so as to deflect electrons toward desired ones of structures 16. In addition to performing an electron-deflection function, electrodes 18 preferably consist of getter material such as an alloy of zirconium, vanadium, and iron.
In FIG. 2, the light-emitting device contains transparent flat substrate 20, transparent electrically conductive layer 22, and phosphor regions 24. Web 26, which may be opaque, laterally surrounds each phosphor region 24. Web 26 may include getter material such as an alloy of zirconium, iron, and aluminum. Additionally or in place of transparent conductive layer 22, the light-emitting device of FIG. 2 may include a thin light-reflective film (not shown), typically aluminum, formed over phosphor regions 24 and web 26. When present, the light-reflective film serves as the display's anode.
The light-emitting device of FIG. 3 contains transparent substrate 28, phosphor regions 30, and electrically conductive material 32 which laterally surrounds each phosphor region 30. Gas-adsorption, i.e., gettering, layer 34 overlies part of conductive material 32. Gas-adsorption layer 34 may be formed by electrophoretically depositing a suspension of the gas-adsorption material through a suitable mask having the desired lateral shape for layer 34.
In FIG. 4, the light-emitting device contains substrate 28, phosphor regions 30, and conductive material 32 arranged as in FIG. 3. Gas-adsorption layer 36 overlies phosphor regions 30 and conductive layer 32 in the device of FIG. 4. Thin retainer layer 38, typically aluminum, overlies phosphor regions 30 and conductive layer 32. Since gas-adsorption layer 36 adjoins phosphor regions 30, layer 36 can sorb contaminant gases emitted by regions 30. U.S. Pat. No. 5,945,780 does not indicate whether retainer layer 38 has passages that enable contaminant gases to pass through layer 38 and be sorbed by layer 36.
Getter material is situated in the active imaging region in each of the prior art getter-containing light-emitting devices of FIGS. 1–4. Hence, each of these devices appears capable of achieving a large getter surface area without significantly increasing the device's overall lateral area. However, the prior art devices of FIGS. 1–4 all have significant disadvantages.
For example, the intensity of light is significantly reduced when it passes through a transparent electrical conductor as occurs in the device of FIG. 1 and typically in the device of FIG. 2. Inasmuch as conductive material 32, which serves as the anode in the display containing the device of FIG. 3, is situated to the sides of phosphor regions 30, the device of FIG. 3 lacks an anode directly in line with regions 30 and therefore appears susceptible to undesired electron-trajectory deflections. Electrons must pass through gas-adsorption layer 36 before striking phosphor regions 30 in the device of FIG. 4, thereby reducing the display's efficiency.
In contrast to the light-emitting devices of FIGS. 1–4, U.S. Pat. No. 5,866,978 discloses an FED in which getter material is situated along the outer wall through which the light-emitting device is coupled to the electron-emitting device. The getter material adjoins both the light-emitting and electron-emitting devices. In the light-emitting device, the getter material overlies a thin peripheral strip of an aluminum layer which extends over phosphor regions. Although the FED of U.S. Pat. No. 5,866,978 avoids many of the disadvantages of the FEDs of FIGS. 1–4, placing getter material only along the outer wall may not yield sufficient getter surface area to achieve long display life.
Somewhat opposite to the light-emitting device of FIG. 4, European Patent Publication (“EPP”) 996,141 discloses a flat-panel CRT display whose light-emitting device contains getter material situated on a light-reflective anode layer which, in turn, overlies fluorescent material in the display's active region. An electrically conductive black matrix, typically in the form of stripes, is situated below the anode layer and thus below the getter material. EPP 996,141 discloses that the getter material can be a blanket layer situated over the entire anode layer. EPP 996,141 also discloses that the getter material can be patterned. When the black matrix consists of stripes, EPP 996,141 discloses that the getter material consists of stripes situated on the anode layer above the black matrix stripes or directly on the black matrix layer apparently in channels extending through the anode layer.
EPP 996,141 specifies that getter material can alternatively or additionally be provided on certain electrical conductors in the electron-emitting device of the flat-panel CRT display. More particularly, EPP 996,141 discloses a surface-conduction flat-panel CRT display in which getter material is situated on row conductors extending over an electrically insulating layer in the electron-emitting device. In an embodiment where row conductors cross over column conductors above the insulating layer, getter material is also provided on exposed portions of the column conductors.
The surface-conduction flat-panel CRT display of EPP 996,141 overcomes some of the disadvantages of the conventional getter-containing flat-panel CRT displays described above. By arranging for getter material to overlie black matrix stripes in the light-emitting device without covering the device's fluorescent material, electrons emitted by surface conduction in the electron-emitting device do not have to pass through that getter material before striking the fluorescent material. The display of EPP 996,141 thus avoids the efficiency loss which occurs in a flat-panel CRT display having the light-emitting device of FIG. 4. However, the density of separate electron-emissive sites is relatively low in the display of EPP 996,141 and can lead to non-uniformities in the display's image intensity.
It is desirable to configure a light-emitting device of a flat-panel display to avoid the foregoing disadvantages yet have getter material positioned so as to achieve high getter surface area without significantly increasing the display's overall lateral area. Similarly, it is desirable to have an electron-emitting device in which getter material is positioned so as to attain high getter surface area in a flat-panel display without causing the display's overall lateral area to significantly increase. It is also desirable that getter material be distributed in a relatively uniform manner across the active portion of the light-emitting or electron-emitting device.